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United States Patent |
5,190,818
|
Sakai
|
March 2, 1993
|
Adhesive composition for temporary adhesive bonding of paper sheets
Abstract
The adhesive composition of the invention exhibits an adequately controlled
adhesive bonding strength when paper sheets coated therewith are bonded
together to be adaptable to subsequent separation of the bonded sheets of
paper by peeling. The essential ingredients of the adhesive composition
include: (a) a rubber latex; (b) a silica gel powder having a specified
average particle diameter; and (c) a starch, preferably, having a
specified particle diameter, e.g. wheat starch, each in a specified weight
proportion. In addition to the good balance between the reliability of the
adhesive bonding and subsequent peelability, the paper sheet coated with
the adhesive composition is prevented from a decrease in the adhesiveness
even when the surface is contaminated with a silicone oil and from the
troubles due to blocking when adhesive-coated sheets are stacked one on
the other with the adhesive-coated surfaces in direct contact with each
other.
Inventors:
|
Sakai; Tsutomu (Tokyo, JP)
|
Assignee:
|
Toppan Moore Co., Ltd. (Tokyo, JP)
|
Appl. No.:
|
672838 |
Filed:
|
March 21, 1991 |
Foreign Application Priority Data
| Apr 20, 1990[JP] | 2-103140 |
| Jun 29, 1990[JP] | 2-170100 |
Current U.S. Class: |
428/355CP; 428/355AC; 428/356; 428/496; 428/511; 428/512; 524/47; 524/492 |
Intern'l Class: |
B32B 007/12; C08L 003/00 |
Field of Search: |
428/356,355
524/47,492
|
References Cited
U.S. Patent Documents
3692713 | Sep., 1972 | Columbus et al. | 524/47.
|
4471082 | Sep., 1984 | Kwok et al. | 524/47.
|
4505976 | Mar., 1985 | Doehnert et al. | 428/355.
|
4568714 | Feb., 1986 | Overholt | 524/47.
|
4576854 | Mar., 1986 | Kurahashi | 428/356.
|
4673698 | Jun., 1987 | Krankkala | 524/47.
|
Foreign Patent Documents |
62-158770 | Dec., 1985 | JP.
| |
62-158771 | Dec., 1985 | JP.
| |
62-158772 | Dec., 1985 | JP.
| |
62-158773 | Dec., 1985 | JP.
| |
Primary Examiner: Lesmes; George F.
Assistant Examiner: Zirker; D. R.
Attorney, Agent or Firm: Wyatt, Gerber, Burke and Badie
Claims
What is claimed is:
1. A peelable adhesive composition which comprises, as a mixture:
(a) an aqueous emulsion or latex of a rubber containing 100 parts by weight
solids:
(b) from 30 to 150 parts by weight of particles of silica gel having an
average particle diameter in the range from 10 nm to 30 .mu.m and an oil
absorption of at least 100 ml/100 g.; and
(c) from 70 to 250 parts by weight of starch having a particle diameter
larger than the average particle diameter of the silica gel particles as
the component (b), the total amount of the comPonents (b) and (c) being in
the range from 100to 400 parts by weight.
2. The adhesive composition as claimed in claim 1 in which the particles of
the starch have an average particle diameter in the range from 5 to 25
.mu.m.
3. The adhesive composition as claimed in claim 1 in which the particles of
silica gel have an average particle diameter in the range from 1 .mu.m to
20 .mu.m.
4. The adhesive composition as claimed in claim 2 in which the starch is
wheat starch.
5. The adhesive composition as claimed in claim 1 in which the rubber is a
natural rubber modified by the graft polymerization of styrene and methyl
methacrylate.
6. The adhesive composition as claimed in claim 5 in which the natural
rubber modified by the graft polymerization of styrene and methyl
methacrylate contains from 2 to 10% by weight and from 10 to 40% by weight
of the styrene moiety and methyl methacrylate moiety, respectively, based
on the moiety of natural rubber.
7. The adhesive composition as claimed in claim 1 in which the silica gel
has an oil absorption ranging from 200 ml/100 g. to 300 ml/100 g.
8. A peelable adhesive-coated paper sheet for temporary adhesive bonding
which is a sheet of paper coated on at least one surface with an adhesive
composition which comprises, as a mixture:
(a) an aqueous emulsion or latex of a rubber containing 100 parts by weight
solids;
(b) from 30 to 150 parts by weight of particles of silica gel having an
average particle diameter in the range from 10 nm to 30 .mu.m and an oil
absorption of at least 100 ml/100 g.; and
(c) from 70 to 250 parts by weight of starch having a particle diameter
larger than the average particle diameter of the silica gel particles as
the component (b), the total amount of components (b) and (c) being in the
range from 100 to 400 parts by weight.
9. The adhesive-coated paper sheet for temporary adhesive bonding as
claimed in claim 8 in which the coating amount of the adhesive composition
is in the range from 2 to 12 g/m.sup.2 as dry.
Description
BACKGROUND OF THE INVENTION
The present invention relates to a novel adhesive composition for temporary
adhesive bonding of paper sheets or, more particularly, the invention
relates to an adhesive composition capable of adhesively bonding sheets of
paper and the like with such an adequate adhesive bonding strength by
pressing without heating of the adhesive layer that the once adhesively
bonded sheets can be separated by peeling without exhibiting an
excessively high peeling resistance.
Along with the revolutionary progress in the information-transmission
systems, the paper-based information-transmission system, such as mailing
of printed matters, is also experiencing an outgrow from its traditional
style. For example, foldable postcards as a system have already been taken
into the acceptable mailing system under the postal law in several
countries. In this system, a sheet of paper having a size substantially
larger than the regular postcard specified by the postal regulations is
printed on the surface and then folded in two or in three by the sender of
the mail with an object to reduce the sheet size to be the regular
postcard size and to keep the printed information in confidence while the
areas on the sheet which come into contact with each other by folding are
coated with a special adhesive so that, when the sheet Is folded and
pressed, the flaps of the folded sheet coming into contact with each other
can be adhesively bonded to each other temporarily enabling the foldable
postcard to be handled in just the same way of mailing as ordinary
postcards and keeping the printed information in confidence. The receiver
of the thus folded postcard separates the adhesively bonded flaps by
peeling into the unfolded sheet so that the printed information on the
theretofore concealed areas by bonding of the flaps is now readable.
Similar foldable sheets of paper are now acquiring prevailing use for
recording and transmitting computerized information printed out by using
various types of printer machines.
As is understood from the above given description of the foldable postcard
system, the performance of the system heavily depends on the properties of
the adhesive with which the foldable postcard is coated on some areas in
order that reliable adhesive bonding can be obtained between the flaps of
the folded sheet at least while the postcard is on the mailing route but
the bonded flaps can be readily opened by the receiver by peeling without
an excessively high peeling resistance eventually to cause rupture of the
paper sheet per se. Namely, the adhesive used in this application,
referred to as a peelable adhesive hereinbelow, must give reliable but
temporary adhesion between sheets of paper. It is known empirically that
the peeling resistance of paper sheets coated with a peelable adhesive
composition and bonded together by pressing should be in the range from 30
to 120 g or, preferably, from 60 to 80 g per 25 mm width although the
exact optimum peeling resistance may depend on the quality of the paper.
Moreover, the surface of a paper sheet coated with a peelable adhesive
composition is sometimes contaminated with a silicone oil in the printing
process, in particular, using a non-impact printer. As is well known,
silicone oils usually give strong surface releasability to the surface
coated or contaminated therewith so that a sheet coated with a peelable
adhesive no longer can exhibit reliable adhesion when the surface is
contaminated with a silicone oil.
It is also important that the surface of the sheet coated with the peelable
adhesive is free from the troubles caused by the phenomenon of so-called
blocking which means that, when adhesive-coated surfaces are kept in
contact with each other, the surfaces spontaneously become bonded together
even without intentional application of a compressive force to effect
bonding by means of the pressure-sensitive adhesive.
Thus, a peelable adhesive must satisfy the two contradictory requirements
for the reliability of adhesive bonding and peelability to ensure safe
opening of the folded sheet by the receiver or reader of the information.
Various types of peelable adhesives have been proposed in the prior art
with an object to control or limit the adhesive bonding strength of the
adhesive composition using a pressure-sensitive, heat-sensitive or
remoistening adhesive as the base adhesive, of which pressure-sensitive
adhesives belong to the only practically promising class as compared with
the other types.
A conventional way to control the adhesive bonding strength of a
pressure-sensitive adhesive is to compound the adhesive with a substantial
amount of a fine solid particulate material although no practically
satisfactory peelable adhesive compositions have yet been obtained by this
means. For example, Japanese patent Kokai 62-158770, -58771, -158772 and
-158773 disclose pressure-sensitive adhesive compositions comprising 100
parts by weight as solid of an emulsion of a synthetic rubber such as SBR,
NBR and polychloroprene rubber, optionary, in combination with a tackifier
and 5 to 40 parts by weight of a fine silica gel powder. These adhesive
compositions, however, are not suitable for use as a peelable adhesive
since no good balance can be obtained therewith between reliability in
adhesive bonding and subsequent peelability.
SUMMARY OF THE INVENTION
The present invention accordingly has an object to provide a novel and
improved peelable adhesive composition capable of giving adhesive-coated
paper sheets which can be temporarily but reliably bonded together by
pressing leaving subsequent peelability with an adequate peeling
resistance and are free from the troubles due to the adhesion-inhibiting
effect by contamination with a silicone oil and due to the phenomenon of
blocking. The invention also has an object to provide a sheet of paper
coated with such a peelable adhesive composition.
Thus, the peelable adhesive composition of the present invention comprises,
as a mixture:
(a) 100 parts by weight as solid of an aqueous emulsion or latex of rubber;
(b) from 30 to 150 parts by weight of particles of silica gel having an
average particle diameter in the range from 10 nm to 30 .mu.m; and
(c) from 70 to 250 parts by weight of starch, the total amount of the
components (b) and (c) being in the range from 100 to 400 parts by weight.
The starch particles should preferably have an average particle diameter in
the range from 5 to 25 .mu.m and the particle diameter of the starch
particles should preferably be larger than that of the silica gel
particles. In this regard, most satisfactory results can be obtained by
using wheat starch as the component (c).
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
As is described above, the essential ingredients in the inventive peelable
adhesive composition include (a) a rubber emulsion or latex, (b) a silica
qel powder and (c) a starch each in a specified amount although it is
optional that the adhesive composition is further admixed with various
kinds of known additives such as tackifiers and the like.
The rubber in the form of an aqueous emulsion or latex as the component (a)
is not particularly limitative including natural rubber, SBR, NBR,
polychloroprene rubber and the like conventionally used as a base
constituent of pressure-sensitive adhesives. It is preferable, however,
that the rubber is a natural rubber modified by the graft polymerization
of styrene and methyl methacrylate in respect of the resistance against
blocking, heat and abrasion of the adhesive-coated surface. The contents
of the styrene moiety and methyl methacrylate moiety in the graft-modified
natural rubber should preferably be in the range from 2 to 10% by weight
and from 10 to 40% by weight, respectively, based on the natural rubber
calculated as solid in the latex. The aqueous emulsion or latex containing
from 40 to 60% by weight of these rubbers are commercially available and
can be used as such or after modification by the graft polymerization as
the component (a) in the inventive peelable adhesive composition.
The component (b) in the inventive adhesive composition is a silica gel
powder which should have an average particle diameter in the range from 10
nm to 30 .mu.m or, preferably, from 1 .mu.m to 20 .mu.m or, more
preferably, from 1 .mu.m to 5 .mu.m. So-called fumed and precipitated
silica fillers such as those commercially available under the tradenames
of Aerosil and the like can also be used as the component (b) with an
object to improve the abrasion resistance of the adhesive layer provided
on a paper sheet although the particles thereof are sometimes too fine to
be used alone.
Another important characteristic parameter of the silica gel powder as the
component (b) is the amount of oil absorption which can be determined, for
example, according to the testing procedure specified in JlS K 5101. This
parameter is particularly important in order to mitigate the adverse
influences caused by the contamination of the adhesive-coated surface with
a silicone oil presumably because the silica gel particles serve to absorb
the silicone oil which otherwise causes a heavy decrease in the
adhesiveness of the surface. In this regard, the silica gel powder as the
component (b) should have an oil absorption of at least 100 ml/100 g or,
preferably, from 200 to 300 ml/100 g.
The amount of the silica gel powder as the component (b) in the inventive
adhesive composition should be in the range from 30 to 150 parts by weight
or, preferably, from 50 to 100 parts by weight per 100 parts by weight of
the rubber latex or emulsion calculated as solid. When the amount of the
silica gel powder is too small, the adhesive bonding strength between the
bonded surfaces would be too high to have the bonded sheets readily peeled
off subsequently in addition to the problem due to the deficiency in the
capacity of oil absorption to prevent the adverse effect caused by the
contamination with a silicone oil. When the amount thereof is too large,
on the other hand, the adhesive bonding strength would be too low so that
the reliability of adhesive bonding is lost to cause eventual spontaneous
separation of the once bonded sheets.
The third of the essential ingredients, i.e. component (c), in the
inventive adhesive composition is a starch. Needless to say, starch is a
natural product obtained from various kinds of plants and the properties
of starches including not only the particle diameter but also morphology
of particles depend on the kind of the plant from which the starch is
obtained. Namely, some of starch particles may be coarse or fine and may
be angular or spherical. Reportedly, the average particle diameters of
starches of various origins are about 30 .mu.m in potato starch, 15 .mu.m
in corn starch, 10 .mu.m in wheat starch, 20 .mu.m in tapioca starch and
15 .mu.m in waxy corn starch. Although it is presumable that the
performance of a starch powder as the component (c) in the inventive
adhesive composition depends on various parameters other than the average
particle diameter and the morphology of particles, the average particle
diameter is the most important parameter according to the results of the
detailed experiments conducted by the inventor. Namely, the starch powder
as the component (c) should have an average particle diameter in the range
from 5 .mu.m to 25 .mu.m or, preferably, from 8 .mu.m to 20 .mu.m. In this
regard, starches of corn, wheat, tapioca and the like can be used as the
component (c) with less Preference of Potato starch, of which most
satisfactory results can be obtained with wheat starch although the exact
reason therefor is not well understood. At least, use of a starch of an
excessively large average particle diameter is undesirable because the
minimum thickness of the adhesive coating layer must be equal to or larger
than the largest particle diameter of the starch particles necessitating a
correspondingly large coating amount.
Importantly, it was discovered that quite satisfactory results could be
obtained when the starch particles as the component (c) had an average
particle diameter substantially larger than that of the silica gel
particles as the component (b). Although the reason therefor is also not
well understood, it is presumable that, when the particle diameter of the
starch is substantially larger than that of the silica gel particles, the
minimum thickness of the adhesive layer formed on the surface of a sheet
is limited by the diameter of the coarser starch particles while the finer
silica gel particles may sink in the adhesive layer between the starch
particles not to appear on the surface of the adhesive layer so that the
possible adverse influences caused by the silicone oil absorbed by and
retained on the surface of the silica gel particles could be further
reduced
The amount of the starch as the component (c) in the inventive adhesive
composition should be in the range from 70 to 250 parts by weight or,
preferably, from 70 to 200 parts by weight or, more preferably, from 120
to 200 parts by weight per 100 parts by weight of the rubber emulsion or
latex as the component (a) calculated as solid provided that the total
amount of the silica gel powder as the component (b) and the starch as the
component (c) is in the range from 100 to 400 parts by weight or,
preferably, from 170 to 300 parts by weight per 100 parts by weight of the
rubber emulsion or latex as the component (a) calculated as solid in view
of the balance between the reliability in the adhesive bonding and
subsequent peelability. When the total amount of these particulate
constituents, i.e. components (b) and (c), in the adhesive composition is
too large, the consistency of the composition would be too high to be
evenly applied on to the surface of a paper sheet. When the total amount
thereof is too small, on the other hand, the adhesive bonding strength
obtained by using the adhesive composition would be too high so that
difficulties are encountered in separating the once adhesively bonded
sheets of paper by subsequent peeling.
The peelable adhesive composition of the present invention comprising the
above described essential components (a), (b) and (c) can be prepared by
merely and uniformly blending the components each in a specified amount
according to a conventional procedure. It is of course optional that the
thus prepared inventive adhesive composition is further admixed with
various known additives including tackifiers such as terpene resins and
the like each in a limited amount.
The peelable adhesive composition of the invention prepared as described
above can be applied to at least one surface of a paper sheet of various
grades by using a conventional coating machine followed by drying with
heating so that an adhesive-coated paper sheet suitable for temporary
adhesive bonding can be obtained. The coating amount is usually in the
range from 2 to 12 g/m.sup.2 or, preferably, from 4 to 8 g/m.sup.2
calculated as dry. The thus adhesive-coated paper sheets can be bonded
together reliably but in a subsequently peelable fashion when they are
laid one on the other with the adhesive-coated surfaces in direct contact
with each other and pressed under an appropriate pressure of, for example,
at least 20 kg/cm.sup.2 at room temperature.
In the following, the peelable adhesive composition of the present
invention and performance of paper sheets coated therewith are illustrated
in more detail by way of examples and comparative examples. The
adhesive-coated paper sheets as the test sample were prepared by coating a
sheet of woodfree paper having a basis weight of 70 g/m.sup.2 on one
surface with the adhesive composition using a wire-bar coater in a coating
amount of 5 g/m.sup.2 as solid followed by drying for 1 minute at 100
.degree. C. and evaluated for the following items in the respectively
described testing procedures.
Test I. Adhesive bonding strength
Two adhesive-coated test sheets were heated for 2 seconds at 180.degree. C.
and, after cooling, they were laid one on the other with the
adhesive-coated surfaces in direct contact with each other and
press-bonded by pressing in a dry sealer under a compressive force of 50
kg/cm.sup.2 at room temperature. The thus adhesively bonded paper sheets
were conditioned by keeping for 30 minutes in an atmosphere of 65%
relative humidity at room temperature and then subjected to the
determination of the Peeling resistance using an automatic tensile tester
(Model Autograph AGS 50, manufactured by Shimadzu Seisakusho Co.) by
pulling in a 90.degree. direction at a pulling velocity of 30 cm/minute at
20 .degree. C.
The results of this peeling-resistance test were given in g per 25 mm width
of the test sample. The results were evaluated to be excellent when the
peeling resistance was from 60 to 80 g/25 mm, good when the peeling
resistance was from 30 to 60 g/25 mm or from 80 to 120 g/25 mm, fair when
the peeling resistance was from 15 to 30 g/25 mm or from 120 to 180 g/25
mm and poor when the peeling resistance was smaller than 15 g/25 mm or
larger than 180 g/25 mm.
Test II. Adhesive bonding strength after contamination with silicone oil
Two adhesive-coated test sheets after heating for 2 seconds at 180.degree.
C. and cooling in the same manner as in Test I were each coated with a
dimethyl silicone oil in a coating amount of 0.5 g/m.sup.2 using a
printability testing machine and then adhesively bonded together also in
the same manner as in Test I excepting an increase of the pressure in the
dry sealer to 100 kg/cm.sup.2.
Thereafter, the thus adhesively bonded sheets were subjected to the
determination of the peeling resistance in the same manner as in Test I
and evaluated according to the same criteria as above.
Test III. Resistance against blocking
Two adhesive-coated test sheets as prepared were laid one on the other with
the adhesive-coated surfaces in direct contact with each other and kept
standing for 30 minutes at 50 .degree. C. under a load of 500 g/cm.sup.2
followed by the determination of the peeling resistance in the same manner
as above. The test sample was evaluated as satisfactory relative to the
resistance against blocking when the peeling resistance determined in the
above described manner did not exceed 10 g/25 mm or, desirably, 5 g/25 mm.
Test IV. Abrasion resistance at elevated temperature
The test was performed according to the procedure specified in JlS P 8136
at a temperature of 150 .degree. C. by rubbing with a metal probe under a
load of 200 to 500 g/cm.sup.2. The test sample was evaluated as
satisfactory when no changes were found on the surface of the adhesive
layer after 20 times of rubbing in the above described manner. When
certain defects were found on the surface of the adhesive layer after
rubbing in a number of times smaller than 20, the number of times of
rubbing, after which certain defects were first found, was recorded.
EXAMPLE 1
A graft-modified natural rubber latex was prepared by conducting emulsion
polymerization of 4 parts by weight of styrene and 16 parts by weight of
methyl methacrylate in a natural rubber latex in an amount of 100 parts by
weight calculated as solid. This rubber latex was admixed with an aqueous
emulsion of a terpene resin as a tackifier in an amount of 5 parts by
weight as solid to give a base adhesive in the form of an aqueous
emulsion, of which the solid content was adjusted to 50% by weight.
Into 100 parts by weight as solid of this base adhesive were added 50 parts
by weight of a silica gel powder having an average particle diameter of
about 4 .mu.m and an oil absorption of 240 ml/100 g and 150 parts by
weight of wheat starch having an average Particle diameter of about 15
.mu.m to prepare a peelable adhesive composition.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are shown in Table 1.
EXAMPLE 2
The experimental procedure was just the same as in Example 1 described
above except that the amount of the wheat starch was increased to 250
parts by weight.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 3
The experimental procedure was just the same as in Example 1 described
above except that the amounts of the silica gel powder and wheat starch
were increased to 100 parts by weight and 200 parts by weight,
respectively.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 4
The experimental procedure was just the same as in Example 1 described
above except that the amounts of the styrene and methyl methacrylate used
in the graft-polymerization for the modification of the natural rubber
latex were increased to 8 parts by weight and 25 parts by weight,
respectively.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 5
The experimental procedure was just the same as in Example 4 described
above except that the amount of the wheat starch was increased to 250
parts by weight.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 6
The experimental procedure was just the same as in Example 4 described
above except that the amounts of the silica gel powder and wheat starch
were increased to 100 parts by weight and 200 parts by weight,
respectively.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
COMPARATIVE EXAMPLE 1
The experimental procedure was just the same as in Example 1 described
above except that the amounts of the silica gel powder and wheat starch
were decreased to 30 parts by weight and 60 parts by weight, respectively.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
COMPARATIVE EXAMPLE 2
The experimental procedure was just the same as in Example 1 described
above except that the amount of the silica gel powder was increased to 60
parts by weight and the amount of the wheat starch was decreased to 30
parts by weight.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
COMPARATIVE EXAMPLE 3
The experimental procedure was just the same as in Example 1 described
above except that the amounts of the silica gel powder and wheat starch
were increased to 200 parts by weight and 250 parts by weight,
respectively.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 7
The experimental procedure was substantially the same as in Example 1
described above except that the base adhesive was prepared by admixing 100
parts by weight as solid of an aliphatic petroleum-based hydrocarbon resin
in the form of an aqueous emulsion containing 46% by weight of solid
(Nopco B-1, a product by Sun Nopco Co.) as a tackifier with 100 parts by
weight as solid of an NBR latex of 40% nitrile ratio containing 41% by
weight of solid (NiPol 516, a product by Nippon Zeon Co.).
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 8
The experimental procedure was substantially the same as in Example 7
described above except that the NBR latex was replaced with the same
amount as solid of an SBR latex of 55% styrene ratio containing 41% by
weight of solid (Nipol LX 204, a product by Nippon Zeon Co.).
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 9
The experimental procedure was substantially the same as in Example 7
described above except that the NBR latex was replaced with the same
amount as solid of a polychloroprene rubber latex containing 50% by weight
of solid (Denka Chloroprene LA-50, a product by Denki Kagaku Kogyo Co.).
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 10
The experimental procedure was substantially the same as in Example 1
described above except that the wheat starch was replaced with the same
amount of potato starch having an average particle diameter of about 30
.mu.m.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 11
The experimental procedure was substantially the same as in Example 10
described above except that the amount of the potato starch was increased
to 250 parts by weight.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 12
The experimental procedure was substantially the same as in Example 10
described above except that the amounts of the silica gel Powder and the
Potato starch were increased to 100 parts by weight and 200 parts by
weight, respectively.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 13
The experimental procedure was substantially the same as in Example 1
described above except that the silica gel powder having an average
particle diameter of 4 .mu.m was replaced with the same amount of another
silica gel powder having an average particle diameter of about 10 .mu.m
and an oil absorption of 220 ml/100 g and the wheat starch was replaced
with the same amount of tapioca starch having an average particle diameter
of about 20 .mu.m.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 14
The experimental procedure was substantially the same as in Example 13
described above except that the amount of the tapioca starch was increased
to 250 parts by weight.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
EXAMPLE 15
The experimental procedure was substantially the same as in Example 13
described above except that the amounts of the silica gel powder and the
tapioca starch were increased to 100 parts by weight and 200 parts by
weight, respectively.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
COMPARATIVE EXAMPLE 4
The experimental procedure was substantially the same as in Example 1
described above except that the silica gel powder having an average
particle diameter of 4 .mu.m was replaced with the same amount of another
silica gel powder having an average particle diameter of about 10 .mu.m
and an oil absorption of 220 ml/100 g and 150 parts by weight of the wheat
starch having an average particle diameter of 15 .mu.m was replaced with
the sane amount of another wheat starch having an average particle
diameter of 4 .mu.m.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
COMPARATIVE EXAMPLE 5
The experimental Procedure was substantially the same as in Comparative
Example 4 described above except that the amount of the wheat starch was
decreased to 50 parts by weight.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
COMPARATIVE EXAMPLE 6
The experimental procedure was substantially the same as in Comparative
Example 4 described above except that the amount of the silica gel powder
was increased to 100 parts by weight and the amount of the wheat starch
was decreased to 20 parts by weight.
The results of the evaluation tests of the thus prepared peelable adhesive
composition are also shown in Table 1.
TABLE 1
______________________________________
Test IV
Test I Test II Test III times of
g/25 mm
g/25 mm g/25 mm rubbing
______________________________________
Example
1 80 75 5.0 >20
2 70 65 2.0 >20
3 60 70 1.5 >20
4 75 70 4.0 >20
5 65 60 1.5 >20
6 60 70 1.0 >20
7 60 45 8.0 >20
8 60 45 8.5 >20
9 70 60 10.0 >20
10 40 30 1.0 15
11 30 20 0.5 15
12 30 15 0 10
13 100 80 5.0 >20
14 80 70 2.0 >20
15 70 70 1.5 >20
Compar-
ative
Example
1 >250 200 40 >20
2 >250 >250 30 >20
3 10 5 0 10
4 20 10 15 >20
5 60 50 40 >20
6 50 55 35 >20
______________________________________
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